RT delta port CE中的∴,port E= 1cc≈sc,
∵在Rt△ADF中∠ mouth AF=大嘴,
∴AF=FD= 1,
∴CD=s8+sc- Da 1=1p,
∴S梯形a口CD = 1s(1p+S8)×da 1 = 77ta(cm)s .